The present invention is to provide a system and method for preventing knocking or fuel knocking in an internal combustion engine.
Fuel knocking or detonation is an uncontrolled second explosion after the spark occurs at the spark plug. Generally, the tendency for an engine to experience detonation increases with an increase of the compression ratio of the engine.
In order to prevent this detonation, a system for retarding the ignition timing is proposed, for example in Japanese patent application laid open 55-19978. However, by such an ignition timing control method, particular conditions exist under which detonation can not be prevented, even if the ignition timing is retarded to a full retard. In order to prevent the detonation in such particular conditions, a spark timing adjusting device must be designed to shift a base ignition timing (such a timing that the pressure during combustion reaches a maximum value at approximately 10.degree. after the top dead center) in the retard direction so as to allow more retardation or designed to increase the range of the retardation in the retard direction. Such a large retardation of the ignition timing causes a decrease of power of the engine and poor fuel consumption.